Why am I not losing weight on Mounjaro? What to check before you change anything

The most common reason the scales are not moving is not that the treatment "does not work for you", but that the period being measured is too short. In the clinical trials, weight loss unfolds over 68-72 weeks, not eight, and the curve has pauses within it. The second most common reason is the way you measure. Only in third place come the explanations that genuinely call for a conversation with the doctor who prescribed your treatment.

This article does not tell you what dose to take and does not discuss administration schedules. Those belong solely to your treating doctor. It tells you what is worth checking before that conversation, so that you arrive with information rather than a feeling.

How much should I lose, realistically?

The figures below come from the trials on the basis of which these medicines were authorised. They are averages at the end of the trial, not individual promises and not a monthly rate.

The SURMOUNT-1 data are published in the New England Journal of Medicine, 2022, and the STEP-1 data in the New England Journal of Medicine, 2021.

Three things are consistently misread in this table:

• The duration. 72 weeks means almost 17 months. If you are in your second month, you are at roughly 12% of the interval over which those figures were produced.
• The average. In SURMOUNT-1, more than 85% of participants in each treatment arm reached a loss of at least 5% of their starting weight. Which means, by the same token, that some did not. The average describes the group, not the person.
• The shape of the curve. Weight loss is not linear. It is faster at first and slows progressively until it approaches a plateau. The plateau is part of the curve, not a deviation from it.

What does "I'm not losing weight" actually mean?

It is worth defining before anything else, because the answer is often "I can't know yet".

A person's weight normally varies by 1-2 kg from one day to the next, for reasons unrelated to body fat: the amount of water in the body, the contents of the gut, the previous day's salt intake, the phase of the menstrual cycle, muscle glycogen after exercise or after a day with more carbohydrates.

This means that a single measurement says almost nothing, and two measurements a week apart say very little. An interval shorter than four weeks, read off the scales, is mostly noise.

If you weigh yourself daily, use the weekly average, not today's figure. If you weigh yourself rarely, do it in the morning, after using the toilet, before breakfast, in the same clothes or none, on the same hard surface. A set of scales placed on a carpet can consistently show something different from the same scales placed on tiles.

And one more thing: weight is not the only thing that changes. Waist circumference, how your clothes fit, blood pressure and blood test results can move during periods when the scales stand still. These are not consolations — they are measurements.

Why does weight loss stop after a few months?

Because the body adapts, and it does so predictably.

A lighter body burns fewer calories — both at rest and for the same effort. The more weight you have lost, the lower your daily requirement compared with the start. The deficit that worked in the first month may no longer exist in the sixth, even though you have changed nothing about what you eat.

Added to this is something less obvious: as nausea and the feeling of early fullness ease over time, food intake rises on its own, without a conscious decision. Portions return to close to what they were before, without anyone feeling that they have "given up".

The plateau is therefore not a sign that the treatment has stopped acting. It is what the curve looks like in its second half. If you want the full picture of what happens in the long term and when the treatment stops, we have written separately about how long the treatment is taken and what comes after.

And what if I'm not losing weight on Wegovy or Ozempic?

Everything above applies in exactly the same way. The active substance differs — semaglutide instead of tirzepatide — but the general mechanism, the shape of the weight-loss curve and the usual reasons for a plateau are the same.

The only difference in the figures is the reference point: in STEP-1, semaglutide 2.4 mg produced an average weight loss of 14.9% at 68 weeks. If you compare yourself with anything, compare yourself with that interval, not with an account on a forum.

A detail that often causes confusion: Ozempic and Wegovy contain the same active substance but have different authorised indications. What the approved document for each says can be read on the pages of the European Medicines Agency — Ozempic and Wegovy.

What do I check at home before I call the doctor?

This list does not replace a consultation. It organises the information for it.

Exactly how many weeks have you been measuring? Write down the date of the first dose and today's date. If the interval is under 4-6 weeks, the most likely answer is "too early".

How are you measuring? The same time, the same scales, the same surface. The weekly average, not the daily figure.

What other medicines do you take? Some classes can favour weight gain — among them certain antidepressants, antipsychotics, corticosteroids, some antiepileptics and certain hormonal treatments. Do not stop or change them on your own. Make a complete list and take it to the consultation.

How much do you sleep? Chronic short sleep is associated with higher food intake the following day. It is one of the few variables that can be changed at no cost.

Do you drink alcohol? The calories from alcohol are easy to underestimate and do not produce a feeling of fullness.

Have you already lost part of your target? If so, a plateau is to be expected rather than surprising — see the section above.

Has anything changed in the last two months? An injury that stopped you moving, a stressful period, a change in your schedule.

What is for the doctor who prescribed my treatment?

Everything to do with the dose, the rhythm of administration and changing the schedule. There is no version in which this is decided from articles, online groups or someone else's experience. The prescribing doctor has your history, your test results and the rest of your medication; no text on the internet does.

What is worth taking to that conversation: the exact measuring interval, the way you measured, the complete list of your current medication, what changed during that period. With this data, the consultation starts from a useful point.

It is also worth raising the question of whether something else is going on. Weight loss that stops abruptly, accompanied by marked tiredness, intolerance to cold, changes in the menstrual cycle or in mood, may have explanations that are investigated with blood tests. They are not assumed — they are looked for.

When should I not wait?

Some situations are not about kilograms and cannot be postponed. Contact your doctor or the emergency services if you have:

• severe, persistent abdominal pain, especially if it spreads to the back;
• repeated vomiting that does not settle, with an inability to keep fluids down;
• signs of severe dehydration — dizziness on standing up, very dark or absent urine, confusion;
• signs of an allergic reaction — a widespread rash, swelling of the face or tongue, difficulty breathing.

The approved product document lists the contraindications and special warnings; for tirzepatide, the official information is published by the European Medicines Agency. We have also summarised them separately in the article on contraindications and situations in which the treatment is not indicated.

In short

• In the clinical trials, the average weight loss takes place over 68-72 weeks; an interval of a few weeks is too short to tell you anything.
• Body weight normally varies by 1-2 kg from one day to the next, so a single measurement cannot distinguish a real plateau from fluctuation.
• The plateau is part of the weight-loss curve: a lighter body burns fewer calories, and the initial deficit closes on its own.
• The dose and the administration schedule are decided solely by the doctor who prescribed the treatment, never on the basis of someone else's experience.
• Severe abdominal pain, vomiting that does not settle and signs of severe dehydration call for an urgent consultation, not adjustments.

This article is for information only and does not replace a medical consultation. Injectable weight-loss treatment is given only on the indication and under the supervision of your treating doctor. Synerva does not prescribe or dispense prescription medicines.